Polycarbonate nanocomposites

ABSTRACT

Nanocomposites comprising a sulfonated telechelic polycarbonate and an organically modified clay are disclosed. The polycarbonate nanocomposites have improved physical and mechanical properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/834,458, filed Aug. 6, 2007. The contents of that disclosure arehereby fully incorporated herein by reference.

The present disclosure is related to the patent application entitled“SULFONATED TELECHELIC POLYCARBONATES,” concurrently filed (Atty. Dkt.No. 220173-1, GEPL 2 00014(I)) as U.S. Ser. No. 11/834,417, now U.S.Pat. No. 7,687,595. The present disclosure is also related to the patentapplication entitled “ACTIVATED ESTERS FOR SYNTHESIS OF SULFONATEDPOLYCARBONATE”, concurrently filed (Atty Dkt. No. 220173-2, GEPL 200014(II)) as U.S. Ser. No. 11/834,437. These disclosures are herebyfully incorporated herein by reference.

BACKGROUND

The present disclosure relates generally to polycarbonate nanocompositesprepared by polymerizing sulfonated telechelic polycarbonates in thepresence of organically modified clays. Processes for producing suchnanocomposites, as well as articles formed from the same, are alsodisclosed.

Nanocomposites are particle-filled polymers for which at least one ofthe dimensions of the dispersed phase is in the nanometer (10⁻⁹ meter)or nanoscale range (typically from about 1 to about 20 nanometers).Nanocomposites often have superior physical and mechanical propertiesover their microcomposite counterparts, such as improved modulus,reduced gas permeability, flame retardance, and improved scratchresistance. Moreover, the nanoscale dispersion of the filler does notgive rise to the brittleness and opacity typical of microcomposites orlarger sized fillers.

Clay-based nanocomposites are obtained by the admixing of extraneousmaterials, such as polymers, with layered clay. Layered clay consists ofmetal silicates that are arranged in layered structures which arestacked in an orderly fashion. Admixing breaks the ordered layering ofthe clay into smaller particles, which are also known as platelets. Theplatelets have the improved properties described above. The clay iseither blended with the polymer or blended with a monomer followed by insitu polymerization.

Polycarbonate nanocomposites have not been extensively researchedcompared to other types of nanocomposites. This may be because of thepoor mechanical and color properties of the polycarbonate nanocompositeswhich have been obtained so far. D. R. Paul reported in Polymer 2003,vol. 44, pp. 5323-5339, that only a small fraction of the clay plateletsare exfoliated while the main part of the polycarbonate/clay compositehas an intercalated morphology. The reason for this low degree ofdispersion may lie in the poor compatibility between the ionic claysurface and the non-polar polymer. As a result of this low degree ofdispersion, the polycarbonate nanocomposite has inferior opticalproperties such as, for example, reduced transparency or increased haze.

D. R. Paul also reported in Polymer 2003, vol. 44, pp. 5341-5354, thatthe polycarbonate/clay composite is generally dark colored and that theweight average molecular weight (Mw) of the polycarbonate matrixconsistently drops by 30% to 40% after extrusion from the melt processused to combine the materials. Typically carried out at about 300° C.,the drop in Mw suggests that the polycarbonate matrix may not bethermally stable.

Furthermore, the color of the nanocomposite may depend on the type andpurity of the clay and on the surfactant used to modify the clay.Ammonium surfactants, commonly used to modify clays during themanufacture of nanocomposites, cannot be used for polycarbonatenanocomposites prepared by melt methods since the thermal stability ofthe resulting clays is below normal processing temperatures forpolycarbonate (280 to 320° C.). This leads to the formation ofdegradation products, providing mechanisms for the consistent decreasein Mw and strong discoloration of the product.

There remains a need for methods that reduce the degradation of thepolymer matrix and increase the degree of dispersion of the clay. Thereis also a need for polycarbonate nanocomposites having improvedthermo-mechanical properties and better color.

BRIEF DESCRIPTION

Disclosed herein, in various embodiments, are nanocomposites comprisinga sulfonated telechelic polycarbonate and an organically modified clay.

In embodiments, the nanocomposite comprises at least one sulfonatedtelechelic polycarbonate and at least one organically modified clay;wherein the sulfonated telechelic polycarbonate comprises sulfonate endgroups and structural units derived from at least one dihydroxy compoundand at least one diaryl carbonate ester.

The nanocomposite may have a degree of dispersion of at least 32angstroms. Additionally, the sulfonated telechelic polycarbonate of thenanocomposite may comprise at least 70 mole percent of sulfonate endgroups, with respect to the total end groups present.

Furthermore, the organically modified clay may be present in thenanocomposite in the amount of from about 0.1 weight percent to about 10weight percent, based on the total weight of the nanocomposite. Theorganically modified clay may be selected from the group consisting ofmontmorillonite, saponite, hectorite, mica, vermiculite, bentonite,nontronite, beidellite, volkonskoite, saponite, magadite, and kenyaite.In specific embodiments, the organically modified clay ismontmorillonite or bentonite.

The organically modified clay may be modified with a functionalizingagent selected from the group consisting of polyalkyl ammonium salts,polyalkyl aminopyridinium salts, polyalkyl guanidinium salts, polyalkylimidazolium salts, polyalkyl benzimidazolium salts, phosphonium salts,sulfonium salts, and mixtures thereof. In specific embodiments, thefunctionalizing agent is a polyalkyl imidazolium salt or a polyalkylbenzimidazolium salt.

In embodiments, articles are formed from a polycarbonate nanocomposite,the nanocomposite comprising at least one sulfonated telechelicpolycarbonate and at least one organically modified clay; wherein thesulfonated telechelic polycarbonate comprises sulfonate end groups andstructural units derived from at least one dihydroxy compound and atleast one diaryl carbonate ester.

In other embodiments, methods for making a polycarbonate nanocompositeare disclosed. For example, the method may comprise:

-   -   reacting an initial mixture comprising at least one dihydroxy        compound, at least one sulfobenzoic acid salt, and an        organically modified clay to obtain an intermediate mixture;    -   adding at least one activated carbonate to the intermediate        mixture; and    -   reacting the intermediate mixture with the activated carbonate        to obtain the polycarbonate nanocomposite.

The dihydroxy compound may have the structure of Formula (I):

wherein R₁ through R₈ are each independently selected from hydrogen,halogen, nitro, cyano, C₁-C₂₀ alkyl, C₄-C₂₀ cycloalkyl, and C₆-C₂₀ aryl;and A is selected from a bond, —O—, —S—, —SO₂—, C₁-C₁₂ alkyl, C₆-C₂₀aromatic, and C₆-C₂₀ cycloaliphatic.

The sulfobenzoic acid salt may have the structure of Formula (II):

wherein M is an alkali metal; Ar″ is an aromatic ring; Q″ is selectedfrom alkoxycarbonyl, halogen, nitro, amide, sulfone, sulfoxide, imine,and cyano; and n″ is a whole number from zero up to the number ofreplaceable hydrogen groups on the aromatic ring Ar″.

The activated carbonate may have the structure of Formula (III):

wherein Q and Q′ are independently selected from alkoxycarbonyl,halogen, nitro, amide, sulfone, sulfoxide, imine, and cyano; Ar and Ar′are independently aromatic rings; n and n′ are independently wholenumbers from zero up to the number of replaceable hydrogen groupssubstituted on the aromatic rings Ar and Ar′, wherein (n+n′)≧1; p and p′are integers; and R and R′ are independently selected from alkyl,substituted alkyl, cycloalkyl, alkoxy, aryl, alkylaryl having from 1 to30 carbon atoms, cyano, nitro, halogen, and carboalkoxy.

The organically modified clay may be present in the amount of about 3weight percent of the initial mixture. The organically modified clay maybe formed in situ during the reaction of the initial mixture.

The initial mixture may be reacted at a temperature of from about 190°C. to about 230° C. The initial mixture may be reacted for a period offrom about 60 minutes to about 120 minutes. The initial mixture may bereacted at a pressure of from about 0.5 bar to about 1.5 bar.

The pressure may be reduced to a range of from about 50 millibar toabout 200 millibar after the activated carbonate is added.

The temperature may be increased to a temperature of from about 250° C.to about 280° C. while the intermediate mixture and the activatedcarbonate are reacted.

The pressure may be reduced to a pressure of from about 0.01 millibar toabout 2 millibar while the intermediate mixture and the activatedcarbonate are reacted.

The intermediate mixture and the activated carbonate may be reacted fora period of from about 30 minutes to about 75 minutes.

In other embodiments, the nanocomposite may comprise at least onesulfonated telechelic polycarbonate and at least one organicallymodified clay; wherein the sulfonated telechelic polycarbonate comprisesstructural units derived from at least one dihydroxy compound and atleast one diaryl carbonate ester; the polycarbonate comprises at least70 mole percent of sulfonate end groups, with respect to the total endgroups present; and the organically modified clay is present in thenanocomposite in the amount of from about 0.1 weight percent to about 10weight percent, based on the total weight of the nanocomposite.

These and other non-limiting characteristics are more particularlydescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a diagram illustrating methods of forming the polycarbonatenanocomposites of the present disclosure.

FIG. 2 is an ¹H-NMR spectrum of a polycarbonate nanocomposite.

FIG. 3 is images of three compositions for comparative purposes.

FIG. 4 is an X-ray diffraction diagram of two nanocomposites forcomparative purposes.

DETAILED DESCRIPTION

The polycarbonate nanocomposites prepared herein can be used in displayfilms, optical applications, automotives, medical and packagingapplications where a combination of properties like transparency,hardness, extension-modulus, scratch resistance, flame retardance, goodmelt flow for moldability, and thermal expansion are required. Otheruses and applications are also contemplated based upon thecharacteristics and properties of the polycarbonate nanocompositesproduced.

The present disclosure may be understood more readily by reference tothe following detailed description of preferred embodiments and theexamples included therein. In the following specification and the claimswhich follow, reference will be made to a number of terms which shall bedefined to have the following meanings.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. All ranges disclosed herein areinclusive of the recited endpoint and independently combinable (forexample, the range of “from 2 grams to 10 grams” is inclusive of theendpoints, 2 grams and 10 grams, and all the intermediate values).

The modifier “about” used in connection with a quantity is inclusive ofthe stated value and has the meaning dictated by the context (forexample, it includes at least the degree of error associated with themeasurement of the particular quantity).

The term “integer” means a whole number which includes zero. Forexample, the expression “n is an integer from 0 to 4” means n may be anywhole number from 0 to 4, including 0.

The term “dispersion” or “dispersed” refers to the distribution of theorganically modified clay particles in the polymer matrix.

“Intercalated” or “intercalate” refers to a higher degree of interactionbetween the polymer matrix and the organically modified clay as comparedto mere dispersion of the organically modified clay in the polymermatrix. When the polymer matrix is said to intercalate the organicallymodified clay, the organically modified clay exhibits an increase in theinterlayer spacing between adjacent platelet surfaces as compared to thestarting organically modified clay.

“Exfoliate” or “exfoliated” refers to platelets dispersed mostly in anindividual state throughout a polymer matrix material. Herein,“exfoliated” is used to denote the highest degree of separation ofplatelet particles. “Exfoliation” refers to the process by which anexfoliate is formed from an intercalated or otherwise dispersedorganically modified clay within a polymer matrix.

“Nanocomposite(s)” and “nanocomposite composition(s)” refer to a polymeror copolymer having dispersed therein a plurality of individual clayplatelets obtained from a layered clay material, wherein the individualplatelets have widths of from about 10 nanometers to about 3000nanometers.

A “telechelic” polymer is a polymer whose end groups are functionalizedwith a suitable organic functional group. Telechelic polymers are wellknown in the literature. Their synthesis and applications have beendiscussed in, for e.g. Odian, G., Principles of Polymerization, 3rdedition, Wiley-Interscience, New York, 1991, pg 427.

The term “end group” refers to the functional group present on the endsof the telechelic polymer chain.

Compounds are described using standard nomenclature. For example, anyposition not substituted by any indicated group is understood to haveits valency filled by a bond as indicated, or a hydrogen atom. A dash(“-”) that is not between two letters or symbols is used to indicate apoint of attachment for a substituent. For example, the aldehyde group—CHO is attached through the carbon of the carbonyl group.

The term “aliphatic” refers to a linear or branched array of atoms thatis not cyclic and has a valence of at least one. Aliphatic groups aredefined to comprise at least one carbon atom. The array of atoms mayinclude heteroatoms such as nitrogen, sulfur, silicon, selenium andoxygen or may be composed exclusively of carbon and hydrogen. Aliphaticgroups may be substituted or unsubstituted. Exemplary aliphatic groupsinclude, but are not limited to, methyl, ethyl, isopropyl, isobutyl,chloromethyl, hydroxymethyl (—CH₂OH), mercaptomethyl (—CH₂SH), methoxy,methoxycarbonyl (CH₃OCO—), nitromethyl (—CH₂NO₂), and thiocarbonyl.

The term “aromatic” refers to an array of atoms having a valence of atleast one and comprising at least one aromatic group. The array of atomshaving a valence of at least one, comprising at least one aromaticgroup, may include heteroatoms such as nitrogen, sulfur, selenium,silicon and oxygen, or may be composed exclusively of carbon andhydrogen. The aromatic group may also include nonaromatic components.For example, a benzyl group is an aromatic group that comprises a phenylring (the aromatic component) and a methylene group (the nonaromaticcomponent). Exemplary aromatic groups include, but are not limited to,phenyl, pyridyl, furanyl, thienyl, naphthyl, biphenyl,4-trifluoromethylphenyl, 4-chloromethylphen-1-yl, and3-trichloromethylphen-1-yl (3-CCl₃Ph-).

The term “cycloaliphatic” refers to an array of atoms which is cyclicbut which is not aromatic. The cycloaliphatic group may includeheteroatoms such as nitrogen, sulfur, selenium, silicon and oxygen, ormay be composed exclusively of carbon and hydrogen. A cycloaliphaticgroup may comprise one or more noncyclic components. For example, acyclohexylmethyl group (C₆H₁₁CH₂) is a cycloaliphatic functionality,which comprises a cyclohexyl ring (the array of atoms which is cyclicbut which is not aromatic) and a methylene group (the noncycliccomponent). Exemplary cycloaliphatic groups include, but are not limitedto, cyclopropyl, cyclobutyl, 1,1,4,4-tetramethylcyclobutyl, piperidinyl,and 2,2,6,6-tetramethylpiperydinyl.

The polycarbonate nanocomposite comprises an organically modified clay.The clay may be natural or synthetic. The clay may be a phyllosilicate.Exemplary clays include, but are not limited to, montmorillonite,saponite, hectorite, mica, vermiculite, bentonite, nontronite,beidellite, volkonskoite, saponite, magadite, and kenyaite. Suitableclays are available from various commercial sources such as Nanocor,Inc., Laviosa Chimica Mineraria, Southern Clay Products, KunimineIndustries, Ltd., and Elementis Specialties, Inc.

Other exemplary clays include: apophyllite, bannisterite, carletonite,cavansite, chrysocolla, delhayelite, elpidite, fedorite, linfurnaceite,gonyerite, gyrolite, leucosphenite, minehillite, nordite, pentagonite,petalite, prehnite, rhodesite, sanbomite; chlorite clays such asbaileychlore, chamosite, general categories of chlorite mineral,cookeite, nimite, pennantite, penninite and sudoite; glauconite, illite,kaolinite, palygorskite, pyrophyllite, sauconite, talc, lepidolite,muscovite, paragonite, phlogopite, zinnwaldite; antigorite [(Mg,Fe)₃Si₂O₅(OH)₄, having a monoclinic structure]; clinochrysotile[Mg₃Si₂O₅(OH)₄, having a monoclinic structure]; lizardite[Mg₃Si₂O₅(OH)₄, having either a trigonal or a hexagonal structure);orthochrysotile [Mg₃Si₂O₅(OH)₄, having an orthorhombic structure]; andparachrysotile [(Mg, Fe)₃Si₂O₅(OH)₄, having an orthorhombic structure].

In specific embodiments, the clay is a smectite clay mineral,particularly bentonite or montmorillonite.

Untreated clays generally have sheet-like structures, due in part to thepresence of rings of tetrahedrons linked by oxygen atoms and shared withother rings in a two dimensional plane. Layers of cations, such assodium ions, connect the sheet-like structures. These layers of cationsthat connect the sheet-like structures are hereinafter referred to asinterlayers. The cations are weakly bonded and are surrounded by neutralmolecules, such as water molecules. The distance between the layers ofsheet-like structures is referred to as the “d-spacing.” The silicon tooxygen ratio in the untreated clay is generally from about 1:1 to about2.5:1. The cohesive energy between interlayers is relatively strong, andunless treated suitably, will not allow the entry of organic polymermolecules between the layers of the untreated clay.

The clay may be converted into an organically modified clay by treatingthe clay with at least one functionalizing agent. This facilitatesseparation of the sheet-like structures into individual plateletparticles. Separating the platelet particles prior to incorporation intothe polycarbonate also improves the polycarbonate/platelet interface.Any treatment that achieves the above goals may be used. Known claytreatments used to modify the clay for the purpose of improvingdispersion of clay materials may be used. This conversion orfunctionalization may be conducted prior to, or during, mixing the claymaterial with the polycarbonate.

Suitable functionalizing agents can increase the d-spacing so as tofacilitate incorporation of polymer molecules. The functionalizing agentalso serves to compatibilize the interlayers of the untreated clay withpolymer molecules to form a polymer nanocomposite. The functionalizationcan be carried out by using functionalizing agents such as imidazolium,phosphonium, ammonium and phthalimide compounds, by employing methodsgenerally known to a person skilled in the art. Typically, thefunctionalization is achieved by a cation-exchange reaction between theuntreated clay and the functionalizing agent. Generally, thefunctionalizing agent is used in an amount that is twice theexperimentally measured exchange capacity of the untreated clay. Thefunctionalizing agent is dissolved in a solvent, such as analcohol-water mixture (e.g., 50:50 v/v) followed by the addition of theuntreated clay. The mixture thus formed is heated for a sufficient timeto obtain an organically modified clay.

Suitable functionalizing agents include, but are not limited to,polyalkyl ammonium salts, polyalkyl aminopyridinium salts, polyalkylguanidinium salts, polyalkyl imidazolium salts, polyalkylbenzimidazolium salts, phosphonium salts, sulfonium salts, and mixturesthereof. Exemplary polyalkyl ammonium salts include tetramethylammonium, hexyl ammonium, bis(2-hydroxyethyl)dimethyl ammonium,octadecyl trimethyl ammonium, bis(2-hydroxyethyl) octadecyl methylammonium, octadecyl benzyl dimethyl ammonium, and the like. Exemplarypolyalkyl aminopyridinium salts include p-dimethylaminoN-methylpyridinium salts, o-dimethylaminopyridinium salts, and the like.Exemplary polyalkyl guanidinium salts include hexaalkyl guanidiniumsalts and the like. Exemplary polyalkyl imidazolium salts includeN,N′-dioctadecyl imidazolium, N,N′-dihexadecyl imiazolium,1,2dimethyl-3-hexadecyl imidazolium, 1-decyl-2,3-dimethyl imidazolium,1-butyl-2,3-dimethyl imidazolium, 1,2-dimethyl-3-propyl imidazolium,1,2-dimethyl-3-hexadecyl imidazolium, N,N′-dioctadecylbenzimidazolium,N,N′-dihexadecylbenzimidazolium, and the like. Exemplary phosphoniumsalts include triphenyldodecyl phosphonium bromide, tributylhexadecylphosphonium bromide, tetraphenyl phosphonium bromide,tetraoctylphosphonium bromide, and the like.

Polyalkyl imidazolium and polyalkyl benzimidazolium salts bearing 1 or 2alkyl chains are particularly preferred functionalizing agents becausethey produce clays with very large d-spacing (over 30 angstroms) andwith thermal stability over 300° C. In some embodiments, the clays havea thermal stability exceeding 350° C.

The polycarbonate nanocomposite further comprises a sulfonatedtelechelic polycarbonate. As used herein, “polycarbonate” refers to anoligomer or polymer comprising residues of one or more dihydroxycompounds joined by carbonate linkages; it also encompassespoly(carbonate-co-ester) oligomers and polymers. Generally speaking, thesulfonated telechelic polycarbonate is the product of the reaction ofthree components: a dihydroxy compound, a sulfobenzoic acid salt, and anactivated carbonate.

The dihydroxy compound has the structure of Formula (I):

wherein R₁ through R₈ are each independently selected from hydrogen,halogen, nitro, cyano, C₁-C₂₀ alkyl, C₄-C₂₀ cycloalkyl, and C₆-C₂₀ aryl;and A is selected from a bond, —O—, —S—, —SO₂—, C₁-C₁₂ alkyl, C₆-C₂₀aromatic, and C₆-C₂₀ cycloaliphatic.

In specific embodiments, the dihydroxy compound of Formula (I) is2,2-bis(4-hydroxyphenyl) propane (i.e. bisphenol-A or BPA). Otherillustrative compounds of Formula (I) include:

-   2,2-bis(3-bromo-4-hydroxyphenyl)propane;-   2,2-bis(4-hydroxy-3-methylphenyl)propane;-   2,2-bis(4-hydroxy-3-isopropylphenyl)propane;-   2,2-bis(3-t-butyl-4-hydroxyphenyl)propane;-   2,2-bis(3-phenyl-4-hydroxyphenyl)propane;-   2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane;-   1,1-bis(4-hydroxyphenyl)cyclohexane;-   1,1-bis(3-chloro-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;-   4,4′ dihydroxy-1,1-biphenyl;-   4,4′-dihydroxy-3,3′-dimethyl-1,1-biphenyl;-   4,4′-dihydroxy-3,3′-dioctyl-1,1-biphenyl;-   4,4′-dihydroxydiphenylether;-   4,4′-dihydroxydiphenylthioether; and-   1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene.

The sulfobenzoic acid salt has the structure of Formula (II):

wherein M is an alkali metal; Ar″ is an aromatic ring; Q″ is selectedfrom alkoxycarbonyl, halogen, nitro, amide, sulfone, sulfoxide, imine,and cyano; and n″ is a whole number from zero up to the number ofreplaceable hydrogen groups on the aromatic ring Ar″. In specificembodiments, the sulfobenzoic acid salt is the 3-sulfobenzoic acid salt(i.e. the sulfonate group is in the meta position to the acid group). Inother specific embodiments, M is sodium, Ar″ is phenyl, and n″ is zero.In this case, the sulfobenzoic acid salt may also be known as the phenylester of the sulfobenzoic acid salt. In other specific embodiments, Ar″is phenyl, n″ is 1, and Q″ is methoxycarbonyl in an ortho position tothe ester bond. In this case, the sulfobenzoic acid salt may also beknown as the methyl salicyl ester of the sulfobenzoic acid salt.

As used herein, the term “activated carbonate” is defined as a diarylcarbonate which is more reactive than diphenyl carbonate towardtransesterification reactions. Such activated carbonates have thestructure of Formula (III):

wherein Q and Q′ are independently activating groups; Ar and Ar′ areindependently aromatic rings; n and n′ are independently whole numbersfrom zero up to the number of replaceable hydrogen groups substituted onthe aromatic rings Ar and Ar′, wherein (n+n′)≧1; p and p′ are integers;and R and R′ are independently selected from alkyl, substituted alkyl,cycloalkyl, alkoxy, aryl, alkylaryl having from 1 to 30 carbon atoms,cyano, nitro, halogen, and carboalkoxy. The number of R groups, p, is aninteger and can be zero up to the number of replaceable hydrogen groupson the aromatic ring Ar minus the number n. The number of R′ groups, p′,is an integer and can be zero up to the number of replaceable hydrogengroups on the aromatic ring Ar′ minus the number n′. The number and typeof the R and R′ substituents on the aromatic rings Ar and Ar′ are notlimited unless they deactivate the carbonate and lead to a carbonatewhich is less reactive than diphenyl carbonate. Typically, the R and R′substituents are located in the para, ortho, or a combination of the twopositions.

Non-limiting examples of activating groups Q and Q′ are: alkoxycarbonylgroups, halogens, nitro groups, amide groups, sulfone groups, sulfoxidegroups, imine groups, and cyano groups.

Specific and non-limiting examples of activated carbonates include:bis(o-methoxycarbonylphenyl)carbonate;

-   bis(o-chlorophenyl)carbonate;-   bis(o-nitrophenyl)carbonate;-   bis(o-acetylphenyl)carbonate;-   bis(o-phenylketonephenyl)carbonate;-   bis(o-formylphenyl)carbonate; and-   bis(o-cyanophenyl)carbonate.    Unsymmetrical combinations of these structures, where the    substitution number and type on Ar and Ar′ are different, may also    be used.

A preferred structure for an activated carbonate is an ester-substituteddiarylcarbonate having the structure of Formula (IV):

wherein R¹ is independently a C₁-C₂₀ alkyl radical, C₄-C₂₀ cycloalkylradical, or C₄-C₂₀ aromatic radical; R² is independently a halogen atom,cyano group, nitro group, C₁-C₂₀ alkyl radical, C₄-C₂₀ cycloalkylradical, C₄-C₂₀ aromatic radical, C₁-C₂₀ alkoxy radical, C₄-C₂₀cycloalkoxy radical, C₄-C₂₀ aryloxy radical, C₁-C₂₀ alkylthio radical,C₄-C₂₀ cycloalkylthio radical, C₄-C₂₀ arylthio radical, C₁-C₂₀alkylsulfinyl radical, C₄-C₂₀ cycloalkylsulfinyl radical, C₄-C₂₀arylsulfinyl radical, C₁-C₂₀ alkylsulfonyl radical, C₄-C₂₀cycloalkylsulfonyl radical, C₄-C₂₀ arylsulfonyl radical, C₁-C₂₀alkoxycarbonyl radical, C₄-C₂₀ cycloalkoxycarbonyl radical, C₄-C₂₀aryloxycarbonyl radical, C₂-C₆₀ alkylamino radical, C₆-C₆₀cycloalkylamino radical, C₅-C₆₀ arylamino radical, C₁-C₄₀alkylaminocarbonyl radical, C₄-C₄₀ cycloalkylaminocarbonyl radical,C₄-C₄₀ arylaminocarbonyl radical, or C₁-C₂₀ acylamino radical; and b isindependently at each occurrence an integer from zero to 4. Preferably,at least one of the substituents CO₂R¹ is attached in an ortho positionrelative to the carbonate group.

Examples of preferred ester-substituted diarylcarbonates include, butare not limited to, bis(methylsalicyl)carbonate (BMSC) (CAS Registry No.82091-12-1), bis(ethyl salicyl)carbonate, bis(propyl salicyl) carbonate,bis(butylsalicyl) carbonate, bis(benzyl salicyl)carbonate, bis(methyl4-chlorosalicyl)carbonate and the like. Typicallybis(methylsalicyl)carbonate is preferred for use in melt polycarbonatesynthesis due to its preparation from less expensive raw materials,lower molecular weight and higher vapor pressure.

One method for determining whether a certain diarylcarbonate isactivated or is not activated is to carry out a modeltransesterification reaction between the certain diarylcarbonate with aphenol such as para-cumyl phenol. This phenol is preferred because itpossesses only one reactive site, possesses a low volatility, andpossesses a similar reactivity to bisphenol-A. The modeltransesterification reaction is carried out at temperatures above themelting points of the certain diarylcarbonate and para-cumyl phenol andin the presence of a transesterification catalyst, which is usually anaqueous solution of sodium hydroxide or sodium phenoxide. Preferredconcentrations of the transesterification catalyst are about 0.001 mole% based on the number of moles of the phenol or diarylcarbonate. Apreferred reaction temperature is 200° C. The choice of conditions andcatalyst concentration can be adjusted depending on the reactivity ofthe reactants and melting points of the reactants to provide aconvenient reaction rate. The only limitation to reaction temperature isthat the temperature must be below the degradation temperature of thereactants. Sealed tubes can be used if the reaction temperatures causethe reactants to volatilize and affect the reactant molar balance. Thedetermination of the equilibrium concentration of reactants isaccomplished through reaction sampling during the course of the reactionand then analysis of the reaction mixture using a well-know detectionmethod to those skilled in the art such as HPLC (high pressure liquidchromatography). Particular care needs to be taken so that reaction doesnot continue after the sample has been removed from the reaction vessel.This is accomplished by cooling down the sample in an ice bath and byemploying a reaction quenching acid such as acetic acid in the waterphase of the HPLC solvent system. It may also be desirable to introducea reaction quenching acid directly into the reaction sample in additionto cooling the reaction mixture. A preferred concentration for theacetic acid in the water phase of the HPLC solvent system is 0.05%(v/v). The equilibrium constant can be determined from the concentrationof the reactants and product when equilibrium is reached. Equilibrium isassumed to have been reached when the concentration of components in thereaction mixture reach a point of little or no change on sampling of thereaction mixture. The equilibrium constant can be determined from theconcentration of the reactants and products at equilibrium by methodswell known to those skilled in the art. A diarylcarbonate whichpossesses an equilibrium constant of greater than 1 is considered topossess a more favorable equilibrium than diphenyl carbonate and is anactivated carbonate, whereas a diaryl carbonate which possesses anequilibrium constant of 1 or less is considered to possess the same or aless favorable equilibrium than diphenyl carbonate and is considered tobe not activated. It is generally preferred to employ an activatedcarbonate with very high reactivity compared to diphenyl carbonate whenconducting transesterification reactions. Preferred are activatedcarbonates with an equilibrium constant at least 10 times greater thanthat of diphenyl carbonate. Use of activated carbonate allowspolymerization in a shorter time and at lower temperatures.

Some non-limiting examples of non-activating groups which, when presentin an ortho position relative to the carbonate group, would not beexpected to result in activated carbonates are alkyl and cycloalkyl.Some specific and non-limiting examples of non-activated carbonates arebis(o-methylphenyl)carbonate, bis(p-cumylphenyl)carbonate, andbis(p-(1,1,3,3-tetramethyl)butylphenyl)carbonate. Unsymmetricalcombinations of these structures are also expected to result innon-activated carbonates.

To form the polycarbonate nanocomposite, an initial reaction mixturecomprising a dihydroxy compound, a sulfobenzoic acid salt, and anorganically modified clay is reacted to obtain an intermediate mixture.The intermediate mixture is then reacted with an activated carbonate toobtain the polycarbonate nanocomposite.

The dihydroxy compound and sulfobenzoic acid salt are first reactedtogether (i.e. separate from the activated carbonate) to improve thesolubility of the salt. In addition, the reaction rate of the activatedcarbonate with the dihydroxy compound is consistently faster than thereaction rate of the sulfobenzoic acid salt with the dihydroxy compound.Thus, in one-pot reactions of the three compounds, the sulfobenzoic acidsalt is unable to react with the dihydroxy compound. As the amount ofunreacted dihydroxy compound decreases, the reaction rate with thesulfobenzoic acid salt also decreases.

The organically modified clay can be made in at least two ways.Untreated clay may be separately modified with a functionalizing agentand then added to the initial reaction mixture. Alternatively, untreatedclay and functionalizing agent may be separately added to the initialreaction mixture and the organically modified clay can be formed in situduring the reaction to form the intermediate mixture. The organicallymodified clay may be present in the amount of from about 0.1 to about 10weight percent of the initial reaction mixture. In specific embodiments,the organically modified clay is about 3 weight percent of the initialreaction mixture.

The molar ratio of dihydroxy compound to sulfobenzoic acid salt can befrom about 99.9:0.1 to about 90:10. In specific embodiments, the molarratio is about 97:3. This ensures a sufficient amount of dihydroxycompound is available to react with the sulfobenzoic acid salt and alsoensures that the sulfobenzoic acid salt becomes a terminal end group.

The initial reaction mixture may further comprise a catalyst. Thecatalyst may be a one-component or multi-component catalyst, such as acatalyst system. In specific embodiments, the catalyst comprises asystem of tetramethyl ammonium hydroxide (TMAH) and sodium hydroxide(NaOH). The weight ratio of TMAH to NaOH can be from about 100 to about500 and, in specific embodiments, is about 263. Other suitable catalystsinclude for use in polycarbonate synthesis include those described inU.S. Pat. Nos. 6,376,640; 6,303,737; 6,323,304; 5,650,470; and5,412,061.

The initial reaction mixture may be reacted at a temperature of fromabout 190° C. to about 230° C. It may be reacted for a period of fromabout 60 minutes to about 120 minutes. It may also be reacted togetherat a pressure of from about 0.5 bar to about 1.5 bar. In specificembodiments, the pressure is atmospheric pressure (1 atm=˜1.013 bar);however, a slight overpressure can be used to decrease the loss of thedihydroxy compound due to evaporation. Generally, the temperature isheld constant during this reaction. In some specific embodiments, theinitial reaction mixture is reacted for 90 minutes at 210° C. atatmospheric pressure. An intermediate mixture results from this firstreaction.

The pressure may be reduced after the activated carbonate is added. Inspecific embodiments, the pressure is reduced to a range of from about50 millibar to about 200 millibar after the activated carbonate isadded.

The intermediate mixture and the activated carbonate may then be reactedfor a period of from about 30 minutes to about 120 minutes.

The temperature and pressure may be varied while the intermediatemixture and the activated carbonate are reacted. The pressure may befurther reduced to a pressure of from about 0.01 millibar to about 2millibar during the reaction. This pressure reduction can be done instages. The temperature may be increased to a temperature of from about250° C. to about 280° C. while the intermediate mixture and theactivated carbonate are reacted. The temperature and pressure may alsobe varied and held at certain levels for certain periods of time duringthis reaction as well.

In specific embodiments, after the activated carbonate is added to themixture, the pressure is reduced to 130 millibar and the intermediatemixture and the activated carbonate are reacted for a period of fromabout 5 minutes to about 30 minutes. The temperature is then increasedto 260° C. while the pressure is further reduced to full vacuum (or asclose as possible) and the reaction is allowed to proceed for anadditional 30 to 45 minutes. The pressure is slowly reduced so that thereaction does not boil too quickly.

A pale yellow and almost transparent nanocomposite is obtained from theprocesses of the present disclosure. The polycarbonates synthesizedusing such methods comprise at least 50 mole percent of sulfonate endgroups, with respect to the total end groups present, or at least 70mole percent. In addition, such polycarbonates do not include sulfonategroups in the backbone of the polycarbonate itself. The addition ofionic groups to the polycarbonate increases the interaction between theclay surface and the polycarbonate, producing better dispersion. Thepolycarbonate nanocomposites of the present disclosure also have goodcolor and good degree of dispersion.

The polycarbonate nanocomposite composition, comprising telechelicsulfonated polycarbonate and organically modified clay, generallycontains the modified clay in the range of from about 0.1 weight percentto about 10 weight percent, based on the total weight of thenanocomposite. In more specific embodiments, the modified clay ispresent in the range of from about 1 weight percent to about 7 weightpercent. In further specific embodiments, the modified clay is presentin the range of from about 2 weight percent to about 5 weight percent.

FIG. 1 is a diagram illustrating the methods of the present disclosure.In this diagram, exemplary compounds BPA, phenyl 3-sulfobenzoate sodiumsalt (3-SBENa), and BMSC are used. BPA, 3-SBENa, and an organicallymodified clay are first reacted together, along with catalyst systemTMAH and NaOH, to form an intermediate mixture. BMSC is then added andreacted with the intermediate mixture to form a telechelic sulfonatedpolycarbonate nanocomposite.

The methods described herein are also applicable to polycarbonates andcopolymers prepared from mixtures and/or combinations of dihydroxycompounds, sulfobenzoic acid salts, activated carbonates, and stableclays. The lower reaction temperatures and shorter polymerization timesconsistently decrease the degradation reactions observed in othermethods.

The polycarbonate/clay nanocomposite compositions may further compriseone or more additives. The additive(s) may be present in quantities ofup to about 80% by weight, and more preferably in quantities of from0.00001 to about 60% by weight, based on the weight of the compositioncomprising the additive(s). These additives include such materials asthermal stabilizers, antioxidants, UV stabilizers, plasticizers, visualeffect enhancers, extenders, antistatic agents, catalyst quenchers, moldreleasing agents, fire retardants, blowing agents, impact modifiers,processing aids, other oligomeric species, and other polymeric species.The different additives that can be incorporated into thepolycarbonate/clay nanocomposites are typically those that are commonlyused in resin compounding and are known to those skilled in the art.

The polycarbonate nanocomposites of the present disclosure may be formedinto articles by conventional plastic processing techniques. Moldedarticles may be made by compression molding, blow molding, injectionmolding or such molding techniques known to those skilled in the art.Articles prepared from the nanocomposites include, but are not limitedto, film, sheet, pipes, tubes, profiles, molded articles, performs,stretch blow molded films and containers, injection blow moldedcontainers, extrusion blow molded films and containers, thermoformedarticles and the like. Articles prepared from the compositions of thepresent disclosure may be used in applications that require materialswith low glass transition temperature and high heat resistance such asautomotive applications. In one embodiment, an article comprises atleast one nanocomposite polymer composition, wherein said compositioncomprises at least one sulfonated telechelic polycarbonate, and at leastone organically modified clay, wherein said telechelic polycarbonatecomprises sulfonate end groups and structural units derived from atleast one diol and at least one carbonate linkage, wherein said articleis an automotive part. Automotive parts are exemplified by body panels,quarter panels, rocker panels, trim, fenders, doors, decklids,trunklids, hoods, bonnets, roofs, bumpers, fascia, grilles, mirrorhousings, pillar appliqués, cladding, body side moldings, wheel covers,hubcaps, door handles, spoilers, window frames, headlamp bezels,headlamps, tail lamps, tail lamp housings, tail lamp bezels, licenseplate enclosures, roof racks, and running boards.

The following examples are provided to illustrate the polycarbonatenanocomposites, articles, and methods of the present disclosure. Theexamples are merely illustrative and are not intended to limit thedisclosure to the materials, conditions, or process parameters set forththerein.

EXAMPLES Example 1

A round bottom wide-neck glass reactor (250 ml capacity) was chargedwith bisphenol-A (BPA) (25.30 grams; 110.8 millimoles), phenyl3-sulfobenzoate sodium salt (3-SBENa) (1.00 grams; 3.32 millimoles),organically modified clay (0.846 grams of a sodium montmorillonite witha Cation Exchange Capacity of 128 milliequivalents/100 grams exchangedwith N,N′-dioctadecyl benzimidazolium salt with a d-spacing of 32angstroms) and the catalyst (a mixture of 2.22×10⁻² millimolestetramethylammonium hydroxide (TMAH) and 8.43×10⁻⁵ millimoles of NaOH).The clay was 3 weight percent of this initial reaction mixture, based onthe weight of the BPA, 3-SBENa, and clay.

The reactor was closed with a three-neck flat flange lid equipped with amechanical stirrer and a torque meter. The system was then connected toa water cooled condenser and immersed in a thermostatic oil-bath at 210°C. and the stirrer switched on at 100 rpm after complete melting of thereactants. After 90 minutes, BMSC (36.95 grams; 111.9 millimoles) wasthen carefully added and dynamic vacuum was applied at 130 millibar for10 minutes. The temperature was then increased to 260° C. over 10minutes and the pressure decreased to 0.2 millibars. The reaction meltwas very viscous after 10 minutes from the application of dynamic vacuumand the stirring was very difficult and slow in the last part of thepolymerization. The very viscous pale yellow and almost transparent meltwas discharged from the reactor and analyzed by ¹H-NMR, GPC, DSC andTGA.

The polymerization was also repeated with other organically modifiedclays and without the addition of ionic groups.

Analysis

FIG. 2 is the ¹H-NMR analysis of the polycarbonate nanocomposite. Noconsistent degradation reaction takes place. No Fries by-products aredetectable by NMR. The end-groups are mainly ionic. However, bothhydroxyl (—OH) and BMSC end groups are still present, not just BMSC endgroups. This may be due to the fact that the melt viscosity was veryhigh and the removal of the methyl salicylate from the BMSC was moredifficult because of the increased barrier properties.

Table 1 shows various properties of three different compositions: thetelechelic sulfonated polycarbonate nanocomposite, the telechelicsulfonated polycarbonate alone (i.e. without clay added), and a BPApolycarbonate nanocomposite (i.e. without sulfonated end groups).

TABLE 1 Clay Ionic Tg Composition (% w/w) Content (%) M_(w) (° C.) TGATelechelic 0 3 44,000 147 409 polycarbonate Polycarbonate 3 0 32,800 142445 nanocomposite Telechelic 3 3 31,400 145 449 nanocomposite

The two nanocomposites had consistently higher thermal stabilitycompared to the telechelic sulfonated polycarbonate, by about 40° C. asseen from the TGA. The telechelic nanocomposite, having ionic groups,was slightly more stable.

No significant differences were observed in DSC analyses. The glasstransition temperatures (Tg) were all in a narrow range and no evidenceof crystallinity was found in any of the samples.

FIG. 3 shows images of thin films (1 millimeter thick) formed from thethree compositions. Improvements in transmittance, clarity, and colorcan be seen for the telechelic nanocomposite compared to thepolycarbonate nanocomposite. The telechelic nanocomposite is brighterthan the polycarbonate nanocomposite, indicating improved transmittance.The image of the seal appears more focused for the telechelicnanocomposite, indicating improved clarity (i.e. decreased haze). Asparticle size decreases, the amount of light they scatter decreases.Thus, improved clarity shows a better dispersion of the clay, i.e. it isexfoliated. The polycarbonate nanocomposite has a brownish color,whereas the telechelic nanocomposite is clear, indicating improvedcolor.

FIG. 4 is an X-ray diffraction diagram of the telechelic nanocompositeand the polycarbonate nanocomposite. The polycarbonate nanocomposite hasa plateau corresponding to a d-spacing of 34 angstroms, as indicated bythe peak. This reflects the distance between layers in the clay andindicates intercalation. In contrast, the telechelic nanocomposite doesnot have this plateau at 34 angstroms. This indicates that the claylayers are no longer stacked, or in other words that the clay isexfoliated.

The polycarbonate nanocomposites of the present disclosure have beendescribed with reference to exemplary embodiments. Obviously,modifications and alterations will occur to others upon reading andunderstanding the preceding detailed description. It is intended thatthe exemplary embodiments be construed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims or the equivalents thereof.

1. A nanocomposite comprising: at least one sulfonated telechelicpolycarbonate; and at least one organically modified clay; wherein thesulfonated telechelic polycarbonate comprises sulfonate end groups andstructural units derived from at least one dihydroxy compound and atleast one diaryl carbonate ester; and wherein the sulfonated telechelicpolycarbonate comprises at least 70 mole percent of sulfonate endgroups, with respect to the total end groups present.
 2. Thenanocomposite of claim 1, wherein the organically modified clay isexfoliated.
 3. The nanocomposite of claim 1, wherein the organicallymodified clay is present in the nanocomposite in the amount of fromabout 0.1 weight percent to about 10 weight percent, based on the totalweight of the nanocomposite.
 4. The nanocomposite of claim 1, whereinthe organically modified clay is selected from the group consisting ofmontmorillonite, saponite, hectorite, mica, vermiculite, bentonite,nontronite, beidellite, volkonskoite, saponite, magadite, and kenyaite.5. The nanocomposite of claim 1, wherein the organically modified clayis montmorillonite or bentonite.
 6. The nanocomposite of claim 1,wherein the organically modified clay is modified with a functionalizingagent selected from the group consisting of polyalkyl ammonium salts,polyalkyl aminopyridinium salts, polyalkyl guanidinium salts, polyalkylimidazolium salts, polyalkyl benzimidazolium salts, phosphonium salts,sulfonium salts, and mixtures thereof.
 7. The nanocomposite of claim 6,wherein the functionalizing agent is a polyalkyl imidazolium salt or apolyalkyl benzimidazolium salt.
 8. An article formed from apolycarbonate nanocomposite, the nanocomposite comprising: at least onesulfonated telechelic polycarbonate; and at least one organicallymodified clay; wherein the sulfonated telechelic polycarbonate comprisessulfonate end groups and structural units derived from at least onedihydroxy compound and at least one diaryl carbonate ester; and whereinthe sulfonated telechelic polycarbonate comprises at least 70 molepercent of sulfonate end groups, with respect to the total end groupspresent.
 9. A method for making a polycarbonate nanocomposite,comprising: reacting an initial mixture comprising at least onedihydroxy compound, at least one sulfobenzoic acid salt, and anorganically modified clay to obtain an intermediate mixture; adding atleast one activated carbonate to the intermediate mixture; and reactingthe intermediate mixture with the activated carbonate to obtain thepolycarbonate nanocomposite.
 10. The method of claim 9, wherein thedihydroxy compound has the structure of Formula (I):

wherein R₁ through R₈ are each independently selected from hydrogen,halogen, nitro, cyano, C₁-C₂₀ alkyl, C₄-C₂₀ cycloalkyl, and C₆-C₂₀ aryl;and A is selected from a bond, —O—, —S—, —SO₂—, C₁-C₁₂ alkyl, C₆-C₂₀aromatic, and C₆-C₂₀ cycloaliphatic; the sulfobenzoic acid salt has thestructure of Formula (II):

wherein M is an alkali metal; Ar″ is an aromatic ring; Q″ is selectedfrom alkoxycarbonyl, halogen, nitro, amide, sulfone, sulfoxide, imine,and cyano; and n″ is a whole number from zero up to the number ofreplaceable hydrogen groups on the aromatic ring Ar″; and the activatedcarbonate has the structure of Formula (III):

wherein Q and Q′ are independently selected from alkoxycarbonyl,halogen, nitro, amide, sulfone, sulfoxide, imine, and cyano; Ar and Ar′are independently aromatic rings; n and n′ are independently wholenumbers from zero up to the number of replaceable hydrogen groupssubstituted on the aromatic rings Ar and Ar′, wherein (n+n′)≧1; p and p′are integers; and R and R′ are independently selected from alkyl,substituted alkyl, cycloalkyl, alkoxy, aryl, alkylaryl having from 1 to30 carbon atoms, cyano, nitro, halogen, and carboalkoxy.
 11. The methodof claim 9, wherein the organically modified clay is formed in situduring the reaction of the initial mixture.
 12. The method of claim 9,wherein the initial mixture is reacted at a temperature of from about190° C. to about 230° C.
 13. The method of claim 9, wherein the initialmixture is reacted for a period of from about 60 minutes to about 120minutes.
 14. The method of claim 9, wherein the initial mixture isreacted at a pressure of from about 0.5 bar to about 1.5 bar.
 15. Themethod of claim 9, wherein the pressure is reduced to a range of fromabout 50 millibar to about 200 millibar after the activated carbonate isadded.
 16. The method of claim 9, wherein the temperature is increasedto a temperature of from about 250° C. to about 280° C. while theintermediate mixture and the activated carbonate are reacted.
 17. Themethod of claim 9, wherein the pressure is reduced to a pressure of fromabout 0.01 millibar to about 2 millibar while the intermediate mixtureand the activated carbonate are reacted.
 18. The method of claim 9,wherein the intermediate mixture and the activated carbonate are reactedfor a period of from about 30 minutes to about 75 minutes.
 19. Themethod of claim 9, wherein Ar″ is phenyl and n″ is zero.
 20. The methodof claim 9, wherein Ar″ is phenyl, n″ is 1, and Q″ is methoxyphenyl inan ortho position to the ester bond.